The next afternoon, Ron, Fred, George, and Harry, who is disguised with Polyjuice Potion as Cousin Barny, prepare to show wedding guests to their seats. Fred grouses about how he won't go to all this trouble when he gets married just as some of Fleur's cousins arrive. Harry shows Lupin and Tonks to their seats and notices again that Lupin looks miserable. When Harry gets back to the entrance, he meets Xenophilius Lovegood, Luna's father. He's dressed eccentrically in bright yellow robes and wears a pendant that looks like an odd, triangular eye. Luna pops up and recognizes Harry through his disguise.
That Harry is aware that something is up with Lupin shows that he's now very tuned in to his community and how they're feeling, even if he doesn't know the reasons why. This indicates that, though Harry still has a long way to go, he's becoming a better friend in that he's getting better at paying attention rather than being too caught up in his own thoughts and emotions to notice what's going on around him.
Ron appears with Auntie Muriel, an ancient witch who is disappointed to meet Cousin Barny, insults Fleur, and suggests that Harry is spineless for not coming. Harry, Ron, and Hermione meet back at the entrance ten minutes later. Hermione looks beautiful but explains that Muriel insisted she had skinny ankles. George joins them and says that Muriel insulted his "lopsided" ears. Viktor Krum arrives. Hermione is ecstatic, but Ron rudely asks Krum why he came. Harry shows Krum to his seat and then sits down. Fleur and Monsieur Delacour come down the aisle, Ginny and Gabrielle behind them. When the ceremony is over, a dance floor appears.
Everything that Harry discovers about Auntie Muriel here should tell him that she's not exactly someone whose thoughts and opinions he should take at face value—she clearly has strong and misguided opinions and is less interested in facts, like that George's ear was cursed off. Krum's attendance at the wedding reminds Harry that he still has an international community if he remembers to call on it.
Ron, Harry, and Hermione join Luna at an empty table. When Luna gets up to dance, Krum takes her seat. He scowls, wants to know who Xenophilius is, and looks even less pleased when Ron drags Hermione to dance. Krum growls at Harry that Xenophilius is wearing the evil wizard Grindelwald's sign. Harry is perplexed; he's sure that Xenophilius doesn't support the Dark Arts. He does a poor job of explaining that the Lovegoods likely don't know what the symbol means and then blurts, "Gregorovitch." Harry remembers that Gregorovitch is the wandmaker who made Krum's wand and thinks that Voldemort is looking for a wandmaker who might know more than Ollivander. Krum strides off.
It's important to remember that as an international wizard, Krum has a very different view on world history than Harry, as a British wizard, will—it's possible that his interpretation of the symbol is colored primarily by the fact that Grindelwald was more active in his country than because of anything to do with what the symbol actually means. This should flag for Harry that he's going to need to think critically about what he learns and recognize that he should engage with information keeping in mind where that information came from.
Later that evening, Harry recognizes Elphias Doge sitting alone, joins him, and reveals his identity. They discuss that Doge knew Dumbledore well, and Harry asks if he saw Rita Skeeter's insistence that Dumbledore was involved in the Dark Arts. Doge tells Harry to not believe it, but Harry isn't reassured—this isn't a matter of belief; Harry wants the truth. As Doge prepares to reassure Harry more, Auntie Muriel joins them, cackling that she needs to pre-order Rita Skeeter's book. She guzzles champagne and accuses Doge of ignoring the darker parts of Dumbledore's past in his obituary. She crows that Dumbledore "did away with his Squib sister," but Doge says that Dumbledore kept her existence quiet because Ariana was unwell. Muriel suggests that Ariana was kept locked in a cellar by Kendra and Dumbledore.
Though Harry's desire for the truth is understandable, it's worth noting that the one person capable of giving Harry the truth—Dumbledore himself—is dead. Furthermore, even if Dumbledore were able to speak to Harry about this, that doesn't mean that Dumbledore's version is the inarguable truth anyway. That Harry doesn't recognize this suggests that he's still fixating on acquiring information that really isn't available to him and, instead, he should do as Doge suggests and figure out how to make sense of Dumbledore's legacy.
Muriel insists that the Dumbledore family kept Ariana a secret because of shame, while Doge insists that Ariana was just unwell. Muriel cackles as she says that Aberforth broke Dumbledore's nose at Ariana's funeral, and Dumbledore didn't defend himself. Harry doesn't know what's true, but he finds it hard to believe that Dumbledore would stand for cruelty in his home. Muriel hiccups that Rita Skeeter surely got the inside scoop from Bathilda Bagshot, who was a close friend of the Dumbledores in Godric's Hollow. Harry chokes on his drink. He's shocked to learn that Dumbledore was also from Godric's Hollow and that he never said anything. Harry feels lied to. Hermione comes over just as Kingsley's lynx Patronus arrives and announces that the Ministry fell and Scrimgeour is dead.
Despite Harry's understandable desire to know the truth about Dumbledore's past, it's also worth keeping in mind that Harry and Dumbledore's relationship was mostly one that centered on Harry's experiences and Dumbledore's ability to pass along knowledge, not an intensely personal relationship that flowed in both directions. That Harry seems to crave that kind of a personal relationship with Dumbledore now that Dumbledore is gone shows how much Harry desires a parent figure in his life.